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Full text of "The manufacture and properties of iron and steel"

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112                         METALLURGY OF IRON AND STEEL.
the other hand, the more rapid action renders possible a lower initial content of silicon, and this is an advantage.
SEC. VIk.—Recarburization.—The method of recarburizing in Bessemer practice varies with the character of the product. In making soft steel, solid ferro containing 80 per cent, of manganese is thrown into the ladle during pouring, the loss of metallic manganese being about 0.2 per cent, of the charge. With rail steel it is customary to add melted spiegel-iron either in the vessel or in the ladle. The loss of manganese depends upon the condition of the bath and upon the amount added. In making soft steel it is necessary to blow until the carbon is reduced to about .05 per cent., and, if manganese be added to the' extent of .60 per cent, of the weight of the charge, the steel will contain .40 per cent., a loss of .20 per cent. If 1.30 per cent, be added, the steel will contain only .90 per cent., a loss of .40 per cent. It seldom happens that soft steel is wanted with over .60 per cent, manganese, but larger proportions are not unusual in rail steel. In the latter case it is feasible to economize by stopping the blow when the carbon is about .10 per cent., and, under these circumstances, an addition of 1.10 per cent, will give 0.90 per cent, in the steel. These figures are approximate, and represent what may be expected in the long run, rather than on any one heat.